Cut zucchini in 1/2-inch slices.,Simmer in water for 10 minutes.,Place in an 8-inch casserole.,Combine the sour cream, Cheddar cheese, butter and salt; heat until blended.,Pour over zucchini.,Combine bread crumbs and grated cheese; sprinkle over casserole.,Bake at 375° for 10 minutes.,______